Leg prosthetics are often costly and complex and the motions effected by many devices now in use are awkward and do not closely approximate the natural walking movement. Many of the devices in use include variable controls which are needed by only a small percentage of amputees. In my prior U.S. Pat. No. 3,316,558 I have disclosed a hydraulic knee control which has a compressed air chamber for applying a predetermined pressure on the hydraulic fluid. A piston with a connecting rod moves through the fluid and has an orifice for allowing fluid to bypass therethrough. In addition, a fixed partition is placed within the fluid with an orifice therein which allows fluid to pass therethrough in response to the piston movement to compress or deflate the compressed air. Although this apparatus is an improvement over its prior art devices, the resistance to deflection and knee extension in this device is substantially the same. However, in real life, one knows that knee flexion and knee extension are not usually equal and opposite forces.